Touch screens are commonly used in many electronic devices and systems to display text and/or modeled objects. They are also known as touch-screens, touchscreens or touch sensitive displays. The user is able to interact with a touch screen through a user interface comprising user interface objects. A touch screen device detects and responds to contact on the touch screen. Thus, the user is able to activate a function, trigger a process or manipulate modeled objects by contacting the touch screen with one finger, several fingers (multi-touch gesture) or a stylus at locations corresponding to the user interface objects he wants to interact with. A user interface object can be a soft key, a menu or a graphic. A gesture can be defined as a sequence of user-interactions for triggering a functionality.
In Natural Sketch the user needs to define a support plane, also called working plane or drawing plane, i.e. the plane on which the sketching is performed. Thus, offering quick ways to select an existing plane, or define a new one is essential. This is the purpose of a specific command, in the product Natural Sketch, for selecting and manipulating a working plane.
On desktop, in this command, there is a plane manipulator that the user can move to define a new plane from the current one. With a left click on an object, the user can select it by pick or by stroke, to retrieve its plane. By using a combination of the middle button and the left/right buttons of the mouse you can navigate in the three-dimensional scene (default CATIA navigation). A selection by stroke may be performed by drawing a continuous curve, that may be visible or not, with a “pointing element” on a screen. All selectable objects intersected by the stroke on the screen are automatically selected.
There are three different kinds of behavior, mapped on three different user actions. We rely on mouse modifiers or buttons (left/middle/right clicks) to differentiate these actions.
On touch only devices (as tablets or smartphones), where there is no button modifier, there is currently no application that allows to simultaneously navigate, manipulate and select an object in a three-dimensional environment.
To resume, in a classic desktop environment, everything works using a mouse:                combination of middle click+left/right click to navigate;        left click on the plane manipulator to move the plane;        left click on an object outside the plane manipulator to select this object and retrieve its plane.        
In the solutions of the state of the art, there are conflicts between gestures which can be quite similar, on the one hand to manipulate the point of view of the scene and on the other hand to select a working plane from a selected object.
It is possible to map each behavior (navigation/manipulation/selection) to a different user action. These actions are simple enough to offer a very intuitive and productive workflow.
On tablet devices, however, the fact that there is no mouse (touch only) implies a number of limitations that impacts this workflow:                No mouse over (moving the mouse without click), thus the user cannot prehighlight the selection; and        No button, thus the user cannot have different behaviors based on which button is clicked. Thus the user cannot have both curve selection and 3D navigation at the same time (achieve with the middle click modifier on desktop).        